Valve for a closed-loop hydraulic torque amplifier

ABSTRACT

A torque amplifier for translating a number of digital input pulses into a proportional angular displacement of a rotary piston and cylinder hydraulic motor. The input pulses drive an electric stepping motor which imparts a linear displacement to a valve. The valve displacement functions to meter fluid into the valve and consequently to the hydraulic motor. The hydraulic motor, through a coupling means, transmits its rotation back to the valve. The valve rotation, first, operates to sequentially distribute the fluid from said valve to the hydraulic motor cylinders, and second, provides a mechanical feedback to displace the valve back to its neutral position.

United States Patent [72] Inventor Jerry D. Wlsbey Lovell-d, 0B0 [21 Appl. No. 830,076 [22] Filed June 3, 1969 [45] Patented Aug. 3, 1971 [73] Assignee TheClndanliMiIhgMachineCo. cud-mom [54] VALVE FOR A CLOSED-D001 HYDRAULIC TORQUE AMPLIFIER 5 Claims, 9 Drawing Figs.

[52] US. 91/503, 91/180, 91/380, 91/448 [51] Int. Cl F011 33/02, FlSb 9/10, F0lb 3/02 [50] FieidofSarch .1 91/175, 380, 180, 375, 35, 448, 503

[56] Reference Cited UNITED STATES PATENTS 3,516,333 6/1970 Jackson 91/380 Primary ExaminerPaul E. Maslousky AnorneysJack J. Earl and Ernst H. Ruf

ABSTRACT: A torque amplifier for translating a number of digital input pulses into a proportional angular displacement of a rotary piston and cylinder hydraulic motor. The input pulses drive an electric stepping motor which imparts a linear displacement to a valve. The valve displacement functions to meter fluid into the valve and consequently to the hydraulic motor. The hydraulic motor, through a coupling means, transmits its rotation back to the valve. The valve rotation, first, operates to sequentially distribute the fluid from said valve to the hydraulic motor cylinders, and second, provides a mechanical feedback to displace the valve back to its neutral position.

PATENTED nus 3197! 3,596,569

' SHEET 1 0F 2 INVENTOR. JERRY D. HKSBEY -J ATTOBN ATENTEU AUG 3 [97,

sum a 2 VALVE FOR A CLOSED-LOOP HYDRAULIC TORQUE AMPLIFIER BACKGROUND There are several hydraulic torque amplifiers known in the art; however, this disclosure recites a unique valve configura tion that provides improved performance and was heretofore unknown. In every hydraulic torque amplifier, two distinct valving functions are required. First, a valve must meter a volume of fluid into the device that is proportional to a number of pulse inputs to the stepping motor. Second, this volume of fluid must be distributed to individual cylinders of a hydraulic motor. This requires two separate and independent valve devices. Typically, the first valving device consists of a spool and sleeve arrangement. An input means produces an axial translation of the spool with respect to the sleeve, causing a volume of fluid to be metered from a source through the valve. Second, this volume of fluid must be sequentially distributed to the hydraulic motor cylinders. The distribution must be timed with the rotation of the motor to obtain maximum power transfer from the motors pistons to an output drive shaft. Consequently, the drive required for this valving section is normally provided by the motor rotation. The valving action is most often accomplished by either plate porting or piston porting means. Applicant proposes a device whereby both valving functions are performed simultaneously by a single valving device. This configuration provides several advantages over a two valve configuration. First, the volume of contained fluid within the device is kept to an absolute minimum. The lower contained volume of fluid provides the motor with a higher natural resonate frequency. This allows a higher system gain and much better system response. Second, with fewer parts, there is a net cost savings and an increase in reliability.

SUMMARY Applicants device has an input means, a hydraulic valve and an output drive all on a common axis of rotation. An electric stepping motor upon receiving a number of input pulses rotates its armature shaft through a precise angular displacement. The armature shaft is coupled to a positioning nut axially fixed but free to rotate about the axis of rotation. A positioning screw is contained in the nut and linearly displaces a distance proportional to the angular displacement of the armature shaft and positioning nut. A valve spool coaxially connected to the positioning screw is contained within a stationary valve sleeve. The spool follows the displacement of the screw and meters a volume of fluid from a source through a first porting means into an annular spool groove. This fluid flows axially through the spool and is distributed by a second porting means having a pintle porting configuration directly into cylinders of the hydraulic motor. For purposes of this disclosure, pintle porting refers to a valving action generated by a rotating member or pintle inside a mating sleeve. The rotation of the pintle controls the flow of fluid between the pintle and the sleeve. The hydraulic action in the motor causes rotation of an output drive shaft which has one end coupled to the valve spool. As the drive shaft turns, the spool and screw rotate to simultaneously perform two operations. First, the valve spool operating as a pintle continues to distribute fluid to the cylinders of the motor. Second, the screw is rotating with respect to the positioning nut and operates to return the spool to its original axial position. Hence, rotation of the motor provides timing for the sequential distribution of fluid to and from the motor cylinders. Fluid is exhausted from the motor by the pintle porting arrangement and is returned through the spool and sleeve to exhaust lines of the source. To summarize, from input pulses fluid is simultaneously ported into the valve and motor by a single hydraulic valving device displacing the motor an amount proportional to the number of input pulses.

DESCRIPTION OF DRAWINGS While the invention has been illustrated in some detail, according to a preferred embodiment shown in the accompanying drawings and while the preferred illustrated embodiment will be described in some detail there is no intention to thus limit the invention to such details. On the contrary, it is intended to cover all modifications, alterations and equivalents falling within the spirit and scope of the appended claims.

FIG. 1 is a longitudinal sectional view of a torque amplifier employing the invention described herein.

FIG. 2 is a vertical sectional view taken along the line 2-2 of FIG. I.

FIG. 3 is an enlarged view of the mechanical summing device used in this apparatus.

FIG. 4, is a partial cross-sectional view of a valve spool.

FIG. 5 through 8 are vertical sectional views taken along lines 5-5, 6-6, 7-7 and 8-8 of FIG. 4.

FIg. 9 is a fragmentary view looking in the direction of arrow 9 in FIG. 4.

DESCRIPTION OF OPERATION FIG. 1 is a longitudinal sectional view illustrating a preferred embodiment of the torque amplifier. The input is provided by a stepping motor 20 which is a commercially available unit. Step increments and torque speed characteristics may be chosen as required by different applications. The input shaft 22 on the output of the motor 20 is coupled to the positioning nut assembly 26 by a coupling 24. Coupling to the nut assembly 26 as opposed to a valve spool reflects the lowest possible inertia back to the input motor. The coupling 24 is a flex-type coupling that allows a small radial misalignment between the coupled axes but maintains a true angular relation between the shaft 22 and the nut assembly 26. The nut assembly 26 is free to rotate about an axis of rotation on thrust bearings 28 but is-restrained from any axial movement by the thrust plate 30 attached to the stationary sleeve 32. A bowed snap ring 34 is used to absorb any end play in the bearing stack 28. A positioning screw 36 is mounted coaxially in the nut assembly 26 and is free to rotate about the rotational axis common to the nut assembly 26 and the shaft 22. The nut assembly 26 and the screw 36 combine to form a motion transformer. A rotation of the nut 26 or first member generating a relative angular displacement between the nut 26 and screw 36 will cause the screw 36 to axially translate. A rotation of the screw 36 or second member decreasing the relative angular displacement between the members will axially translate the screw 36 in the opposite direction. The nut assembly 26 is of an antibacltlash construction. In FIG. 3 a first nut 38 contains a tapered bearing surface 40, straight threads 42 and axial slots 44 in the threads 42. The nut 38 is engaged with the screw 36. A cap nut 46 containing an internal tapered bearing surface 48 is screwed onto the nut 38. As the cap nut 46 is tightened, the slots 44 allow the forces applied at the bearing surfaces 40 and 48 to flex that end of the nut 38 onto the screw 36. Consequently, backlash between the nut assembly 26 and the screw 36 is reduced to a practical minimum.

Returning to FIG. 1, rigidly connected to the positioning screw 36 is a valve spool 50 coaxially mounted about the axis of rotation. Hg. 4 is a partial cross-sectional view of the valve spool 50. Positioned at various axial points on the spool are small annular balancing grooves 52. These grooves 52 help maintain an equal radial pressure distribution along the length of the spool 50. A larger annular groove 54 is placed in fluidic communication with a first pintle porting section by a first axial blind hole 56. FIG. 5 is a cross section at this point. Also shown is an axial drain hole 58 passing through the spool. The drain hole 58 operates to relieve any hydraulic pressure differentials that may exist on the spool end faces. FIG. 4 shows an annular drain groove 60 approximately centrally located along the axis of the spool 50 and connected with the hole 58 by a radial passage 61. The purpose of the groove 60 is to help relieve any radial pressure differentials. A second larger annular groove 62 is placed in fluidic communication'with a second pintle porting section by a second axial blind hole 64. FIG. 6 is a cross section further clarifying the valve construction at this point. The axial holes 56 and 64 are connected to first and second arcuate grooves 66 and 68 by first and second passages 70 and 72 as shown in FIG. 9. FIG. 8 is a crosssection centrally taken in the pintle porting area and clarifies the pintle porting configuration. FIG. 9 shows a first and second pair of arcual balancing grooves 74 and 76. These are necessary to balance the radial forces caused by the pressure differential across the two pintle porting section. For example, if the first groove 66 is used to supply fluid under pressure and the second groove 68 is used as an exhaust line, the pressure differential across the spool will generate a substantial radial force. This will tend to deflect or cock the spool 50 in its mating sleeve 32. To overcome this problem, the two pairs of arcual balancing grooves 74 and 76 are used. FIG. 7 is a cross section taken through one of the grooves in each of the pair of grooves 74 and 76. In this figure, groove 74 is connected to A hole 56 by a first passage 78; and groove 76 is connected to hole 64 by a second passage 80. Likewise the other of the grooves of the pairs of grooves 74 and 76 are connected to the holes 56 and 64 respectively. Hence, any radial force produced by pressure in groove 66 will have an equal but opposite force generated in the first pair of grooves 74. Also any radial force produced in groove 68 is offset by radial forces produced in the second pair of grooves 76.

The spool 50 is totally contained within a coaxially mounted stationary sleeve 32. In FIG. 1, the sleeve contains several pairs of opposed internal ports defined by the radial openings 82. Each pair of ports is adjacent to a corresponding annular body groove 84 in the valve body 86. The pairs of ports 82 and the lands 83 on the valve spool 50 provide the first valving action upon axial translation of said spool 50. At the other end of the sleeve 32 are radial holes 88, also shown in FIG. 2, and circumferentially spaced to complete the pintle porting. Each radial hole 88 is positioned to match a corresponding motor cylinder and is connected by a straight radial passage through the body 86. In FIG. 1 a rotary piston and cylinder hydraulic motor 90 is coaxially positioned about one end of the spool and sleeve assembly. An output shaft 92 of the motor 90 is coupled to one end of the spool 50 through a feed back coupling 94. The coupling 94 allows an axial translation of the spool 50 with respect to the motor shaft 92, but it maintains an accurate angular relation between the two members. Any rotation of the output shaft 92 is imparted to the valve spool 50 and provides a driving force for the pintle porting. FIG. 2 best illustrates this action. Assume, for example, that the hole 56 supplies fluid under pressure. This will cause a counterclockwise rotation of the motor shaft 92 and the spool 50. As the spool 50 rotates, the porting area 66 sequentially supplies fluid under pressure to several of the motor cylinders. The porting area 68 receives exhaust fluid from other cylinders. As in other hydraulic motors, the timing between the porting of fluid under pressure and the position of the piston in the cylinder is critical. The pressure must be initially applied just after the piston has passed its lowest position in the motor cylinder. This timing between the motor and the valving means is established in manufacturing of the apparatus and remains fixed thereafter. It should be noted at this point that FIG. 2 shows a hydraulic motor with an even number of pistons and cylinders. It is well known to those skilled in the art that such a device is operable but undesirable. An even number was chosen for ease of illustration. The apparatus disclosed can be adapted to any number of pistons and cylinders as required by a particular hydraulic motor.

Returning to FIG. I, in operation, the stepping motor receives electrical input pulses from an external source. Each pulse represents a discrete linear displacement of a movable element coupled to the hydraulic motor output. For each input pulse received, the stepping motor 20 drives its output shaft 22 through a precise angular displacement. This results in an identical displacement of the positioning nut assembly 26 and a proportional axial translation of the screw 36 and the valve spool 50. Assume the stepping motor 20 is rotated in a counterclockwise direction as viewed from the left end of said motor. This results in an axial translation of the positioning screw 36 and the valve spool 50 towards the right. The axial translation of the spool 50 generates a first and second pair of orifices at points 96 and 98 between the internal ports 82 of the valve sleeve 32 and the corresponding lands 83 on'the valve spool 50. Fluid enters the motor through input port 100, passes through an annular body groove 84, and is metered through a first pair of orifices at point 96 into the annular groove 54. The axial hole 56 ports the fluid to the pintle porting area 66, shown in FIG. 2, which distributes the fluid through the radial holes of the valve sleeve 32 and the body 86 into the corresponding motor cylinders. The fluid pressure forces a piston identical to the piston 102 shown in FIG. 1 outward against the piston thrust plate 104. The thrust plate 104 transmits this force through the wobble thrust bearing 106 to the wobble portion of the hydraulic motor shaft 92. This rotates the output shaft 92 in the same direction the stepping motor rotated. As the hydraulic motor shaft 92 rotates, other pistons are being forced into their bores by the piston thrust plate 104. This action displaces fluid through their corresponding radial sleeve holes 88 into the pintle porting section 68. The fluid passes through the axial hole 64 into the annular groove 62 and out the second pair of orifices at the point 98. It is then exhausted out an annular body groove 84 and exhaust port 108 back to the fluid source. One end of the hydraulic motor shaft 92 is coupled to the valve spool 50. As the output shaft 92 and the valve spool 50 rotate, the positioning screw 36 rotates. Assume the stepping motor 20 is still providing a constant angular velocity to the nut assembly 26. The feedback from the motor shaft rotation will drive the screw 36 at the same angular velocity, and the screw 36 will maintain a constant axial position with respect to the nut assembly 26. Assume now the input from the stepping motor 20 ceases. The hydraulic motor will continue to rotate providing a feedback to the spool 50in the screw 36. The rotation of the screw 36 in the stationary nut assembly 26 axially translates the screw 36 and the spool 50 back to their original positions closing the orifices at points 96 and 98.

What I claim is:

1. An improved torque amplifier of the type comprised in part of a hydraulic motor being powered by fluid from a source and driven through an increment of motion in accordance with an angular displacement of an input shaft, wherein the improvement comprises:

a. a hydraulic valve comprised of a rotatable spool adapted inside a stationary member, said spool being coupled l. at one end to the input shaft and responding to the angular displacement by axially translating a distance proportional to a relative angular displacement between the input shaft and the spool, and

2. at the other end to the hydraulic motor for rotating with the motor and decreasing the relative angular displacement between the input shaft and the spool;

b. means connected to the source for metering fluid between the source and the valve in response to the axial translation of the spool; and

c. means fluidally connected to the metering means for providing a timely and direct distribution of fluid between the valve and the hydraulic motor in response to the spool rotation.

2. An improved torque amplifier of the type comprised in part of a rotary piston and cylinder hydraulic motor being powered by fluid from an external source and having a drive shaft rotated about an axis through an increment of motion in accordance with an angular displacement of an output shaft of an electric stepping motor responding to a number of electrical input pulses, wherein the improvement comprises:

a. a hydraulic valve comprised of a rotatable spool inside a stationary sleeve and coaxially mounted about the axis, said valve including 1. a first porting means operating upon an axial translation of the spool relative to the sleeve for metering fluid between the external source and the valve, and

2. a second porting means in fluidic communication with the first porting means and operating upon a spool rotation;

. a motion transformer comprising a first member connected to the output shaft and in mechanical communication with a second member connected to one end of the spool, said transformer producing an axial translation of the spool in response to a rotation of the output shaft generating a relative angular displacement between the members; and

. means for coupling the other end of the spool to the drive 3. The apparatus of claim 2 wherein the motion transformer further comprises:

a. a threaded nut defining the first member and rotatably mounted about the axis, said nut rotating with the output shaft with no angular error but being restrained from having any axial movement,

b. a screw defining the second member and in threaded engagement within the nut, said screw being rigidly con nected to the rotatable spool, and

the second porting means.

5. An improved torque amplifier of the type comprised in part of a rotary piston and cylinder hydraulic motor being powered by fluid from a source and having a drive shaft rotated about an axis through an increment of motion in accordance with an angular displacement of an output shaft of an electric stepping motor responding to a number of electrical input pulses, wherein the improvement comprises:

a. a threaded nut coupled to said output shaft and axially fixed about the axis to rotate through the angular displacement;

b. a threaded screw rotatably mounted within the nut about the axis, said screw axially translating a distance proportional to a relative angular displacement between the screw and nut;

c. a cylindrical stationary sleeve coaxially mounted on the axis and including 1. a plurality of sets of radial openings, and 2. a plurality of holes;

d. a cylindrical spool rotatably mounted in the stationary sleeve and rigidly connected at one end to the threaded screw and including 1. a pair of annular grooves, upon the spool axially translating, one of the annular grooves receives fluid under pressure from the source through one of the sets of radial openings in the sleeve and the other of the annu-' lar grooves exhausts fluid to the source through another of the sets of radial openings,

2. two opposed arcuate grooves, upon the spool rotating,

one of the arcuate grooves supplies fluid under pressure to the hydraulic motor cylinders through a number of the radial holes in the sleeve, and the other of the arcuate grooves receives fluid from the hydraulic motor c. means adapted between the nut and screw for removing cylinders through other of the radial holes, and

backlash. 3. two internal passages within the spool, one of the 4. The apparatus of claim 2 wherein said hydraulic valve passages connecting one of the annular grooves with further comprises: one of the arcuate grooves, and the other of the passages connecting the other of the annular grooves with the other of the arcuate grooves; and means for coupling the other end of the spool to the output drive shaft of the hydraulic motor and transmitting the rotation of the motor to the spool and screw, said screw rotation being operative to decrease the relative angular displacement between the screw and nut and reverse the axial translation of the screw thereby interrupting the supply of fluid between the source and the annular grooves in the spool.

a. a first set of openings in the sleeve and annular lands on the spool for establishing the first porting means and metering fluid between the source and annular grooves in the spool,

b. a second set of openings in the sleeve and arcuate grooves in the spool for establishing the second porting means and distributing fluid between the spool and the motor cylinders, and l c. means for providing passages in the spool between the annular grooves and the arcuate grooves for transmitting fluid within the spool between the first porting means and 

1. An improved torque amplifier of the type comprised in part of a hydraulic motor being powered by fluid from a source and driven through an increment of motion in accordance with an angular displacement of an input shaft, wherein the improvement comprises: a. a hydraulic valve comprised of a rotatable spool adapted inside a stationary member, said spool being coupled
 1. at one end to the input shaft and responding to the angular displacement by axially translating a distance proportional to a relative angular displacement between the input shaft and the spool, and
 2. at the other end to the hydraulic motor for rotating with the motor and decreasing the relative angular displacement between the input shaft and the spool; b. means connected to the source for metering fluid between the source and the valve in response to the axial translation of the spool; and c. means fluidally connected to the metering means for providing a timely and direct distribution of fluid between the valve and the hydraulic motor in response to the spool rotation.
 2. at the other end to the hydraulic motor for rotating with the motor and decreasing the relative angular displacement between the input shaft and the spool; b. means connected to the source for metering fluid between the source and the valve in response to the axial translation of the spool; and c. means fluidally connected to the metering means for providing a timely and direct distribution of fluid between the valve and the hydraulic motor in response to the spool rotation.
 2. An improved torque amplifier of the type comprised in part of a rotary piston and cylinder hydraulic motor being powered by fluid from an external source and having a drive shaft rotated about an axis through an increment of motion in accordance with an angular displacement of an output shaft of an electric stepping motor responding to a number of electrical input pulses, wherein the improvement comprises: a. a hydraulic valve comprised of a rotatable spool inside a stationary sleeve and coaxially mounted about the axis, said valve including
 2. a second porting means in fluidic communication with the first porting means and operating upon a spool rotation; b. a motion transformer comprising a first member connected to the output shaft and in mechanical communication with a second member connected to one end of the spool, said transformer producing an axial translation of the spool in response to a rotation of the output shaft generating a relative angular displacement between the members; and c. means for coupling the other end of the spool to the drive shaft for imparting a rotary motion of the hydraulic motor to the spool, said spool rotation providing
 2. a transmission of the motor rotation to the second member for decreasing the relative angular displacement between said members and restoring the spool to its original axial position.
 2. a plurality of holes; d. a cylindrical spool rotatably mounted in the stationary sleeve and rigidly connected at one end to the threaded screw and including
 2. two opposed arcuate grooves, upon the spool rotating, one of the arcuate grooves supplies fluid under pressure to the hydraulic motor cylinders through a number of the radial holes in the sleeve, and the other of the arcuate grooves receives fluid from the hydraulic motor cylinders through other of the radial holes, and
 3. two internal passages within the spool, one of the passages connecting one of the annular grooves with one of the arcuate grooves, and the other of the passages connecting the other of the annular grooves with the other of the arcuate grooves; and e. means for coupling the other end of the spool to the output drive shaft of the hydraulic motor and transmitting the rotation of the motor to the spool and screw, said screw rotation being operative to decrease the relative angular displacement between the screw and nut and reverse the axial translation of the screw thereby interrupting the supply of fluid between the source and the annular grooves in the spool.
 3. The apparatus of claim 2 wherein the motion transformer further comprises: a. a threaded nut defining the first member and rotatably mounted about the axis, said nut rotating with the output shaft with no angular error but being restrained from having any axial movement, b. a screw defining the second member and in threaded engagement within the nut, said screw being rigidly connected to the rotatable spool, and c. means adapted between the nut and screw for removing backlash.
 4. The apparatus of claim 2 wherein said hydraulic valve further comprises: a. a first set of openings in the sleeve and annular lands on the spool for establishing the first porting means and metering fluid between the source and annular grooves in the spool, b. a second set of openings in the sleeve and arcuaTe grooves in the spool for establishing the second porting means and distributing fluid between the spool and the motor cylinders, and c. means for providing passages in the spool between the annular grooves and the arcuate grooves for transmitting fluid within the spool between the first porting means and the second porting means.
 5. An improved torque amplifier of the type comprised in part of a rotary piston and cylinder hydraulic motor being powered by fluid from a source and having a drive shaft rotated about an axis through an increment of motion in accordance with an angular displacement of an output shaft of an electric stepping motor responding to a number of electrical input pulses, wherein the improvement comprises: a. a threaded nut coupled to said output shaft and axially fixed about the axis to rotate through the angular displacement; b. a threaded screw rotatably mounted within the nut about the axis, said screw axially translating a distance proportional to a relative angular displacement between the screw and nut; c. a cylindrical stationary sleeve coaxially mounted on the axis and including 